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Can you use a 5v DC adapter rated about 300 ma instead of a 4.5 v. DC adapter on a CD player?

Discussion in 'General Electronics Discussion' started by ezymel, Aug 3, 2017.

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  1. ezymel


    Aug 3, 2017

    I have a portable CD player which requires a 4.5 v. dc source. There are two 1.5 v. batteries which power the unit. Since I can plug in 4.5 volts, I imagine that it is further reduced by diodes which is still a regulated power source. I thought of adding a resistor to a 5v adapter but it would be unregulated causing some problems in the player. My question is: Can I use a 5v dc adapter which I have plenty? We are looking at a .5 v difference. Can that pose a problem? Thanks for y our response?
    Last edited by a moderator: Aug 3, 2017
  2. davenn

    davenn Moderator

    Sep 5, 2009
    adding a resistor wont work

    if it is not a regulated plug pack, then the CD player is likely to get much more than 5V if it isn't drawing 300mA

    if it is regulated then used a diode in the positive line to drop 0.5V

    what does the label on the CD play state for current rating ?
  3. Terry01


    Jul 5, 2017
    Sorry for jumping in on your question but I was scrolling through and it caught my attention. I would never have replied as I don't know the answer. But.......the part I have picked up so far for my bench PSU is if your CD only needs 4.5v and you set the psu to 5v the CD will take the 4.5v it needs and that's it. Does it only do this if its a regulated power supply? Does the 5v 300ma rated psu mean this is its optimum operating setting but it will give more v to try and keep the 300ma rather than the 4.5v the CD needs with the A just falling in to whatever the CD will take comfortably without cooking? I'm still trying to get my head round constant currant and constant voltage.
  4. davenn

    davenn Moderator

    Sep 5, 2009
    you have missed the point of my question back to the OP about how much current the player needs

    and no it will take for full 5V ... why wouldn't it ? that is what it is being supplied with

    using your analogy, it would mean you could replace your 12V car battery with a 24V one from a truck and it would work ... NO... things will get cooked

    no, if the PSU is an unregulated 5V ( or whatever) one, it's open circuit voltage will be much higher for a 5V one it could easily be ~ 10V. A 12V one can easily be outputting 16V when open circuit.
    An unregulated 5V 300mA supply will only be putting out 5V when 300mA is being drawn from it

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